﻿AGE 
  OF 
  THE 
  EARTH 
  — 
  CHAMBERLIN 
  AND 
  OTHERS. 
  249 
  

  

  those 
  that 
  arise 
  from 
  surface 
  action. 
  Account 
  must 
  also 
  be 
  taken 
  of 
  

   such 
  reversals 
  of 
  action 
  as 
  take 
  material 
  out 
  of 
  solution 
  and 
  return 
  

   it 
  to 
  the 
  solid 
  state. 
  All 
  these 
  must 
  be 
  considered, 
  for 
  they 
  are 
  all 
  

   necessarily 
  involved 
  in 
  the 
  question 
  of 
  the 
  age 
  of 
  the 
  ocean. 
  Some 
  

   basal 
  assumptions 
  are 
  unavoidable, 
  and 
  if 
  we 
  must 
  deal 
  with 
  them 
  

   it 
  is 
  best 
  to 
  be 
  frank 
  and 
  explicit 
  about 
  them. 
  The 
  necessary 
  as- 
  

   sumptions 
  as 
  to 
  the 
  early 
  stages 
  of 
  the 
  ocean 
  are 
  more 
  or 
  less 
  specu- 
  

   lative, 
  but 
  if 
  we 
  are 
  to 
  discuss 
  the 
  question 
  of 
  age 
  at 
  all, 
  there 
  is 
  no 
  

   occasion 
  to 
  be 
  squeamish 
  about 
  that. 
  It 
  does 
  not 
  make 
  the 
  assump- 
  

   tions 
  any 
  less 
  " 
  speculative 
  " 
  to 
  gloss 
  over 
  or 
  shy 
  at 
  the 
  fact 
  that 
  

   they 
  are 
  speculative 
  or 
  at 
  least 
  have 
  speculative 
  factors. 
  Assump- 
  

   tions 
  are 
  least 
  dangerous 
  when 
  explicitly 
  recognized. 
  They 
  are 
  

   even 
  likely 
  to 
  be 
  least 
  speculative 
  when 
  the 
  grounds 
  on 
  which 
  they 
  

   rest 
  are 
  carefully 
  sifted, 
  logically 
  weighed, 
  and 
  made 
  to 
  throw 
  such 
  

   light 
  as 
  they 
  may 
  on 
  the 
  question 
  in 
  hand. 
  We 
  have 
  no 
  call 
  to 
  dis- 
  

   cuss 
  the 
  age 
  of 
  the 
  ocean 
  at 
  all 
  unless 
  we 
  are 
  ready 
  to 
  be 
  frank 
  about 
  

   the 
  other 
  end 
  of 
  its 
  history. 
  The 
  crux 
  of 
  the 
  issue 
  lies 
  there. 
  We 
  

   are 
  all 
  agreed 
  about 
  the 
  age 
  of 
  this 
  end. 
  

  

  The 
  two 
  types 
  of 
  assumptions 
  in 
  actual 
  use 
  and 
  their 
  radical 
  

   differences. 
  14 
  — 
  Only 
  two 
  general 
  types 
  of 
  assumptions 
  require 
  recog- 
  

  

  14 
  The 
  four 
  estimates 
  of 
  the 
  age 
  of 
  the 
  ocean 
  which 
  were 
  cited 
  earlier 
  arid 
  which 
  give 
  

   an 
  average 
  age 
  of 
  95,000,000 
  years, 
  with 
  a 
  range 
  from 
  70,000,000 
  to 
  150,000,000 
  years, 
  

   seem 
  clearly 
  to 
  have 
  been 
  made 
  on 
  the 
  basis 
  of 
  the 
  inherited 
  view 
  of 
  the 
  origin 
  of 
  the 
  

   earth. 
  This 
  assumes 
  that 
  all 
  the 
  material 
  of 
  the 
  present 
  hydrosphere, 
  together 
  with 
  

   such 
  substances 
  of 
  the 
  present 
  earth 
  body 
  as 
  would 
  be 
  volatile 
  at 
  the 
  temperature 
  of 
  

   molten 
  rock, 
  were 
  held 
  in 
  the 
  atmosphere 
  which 
  surrounded 
  the 
  supposed 
  molten 
  earth. 
  

   The 
  oceanic 
  history 
  is 
  assumed 
  to 
  have 
  begun 
  when 
  the 
  waters 
  from 
  this 
  primitive 
  ocean- 
  

   bearing 
  atmosphere 
  condensed 
  upon 
  the 
  crust 
  that 
  had 
  formed 
  over 
  the 
  molten 
  earth. 
  

   The 
  great 
  influence 
  which 
  this 
  view 
  kas 
  had 
  on 
  geologic 
  thought 
  and 
  the 
  wide 
  extent 
  to 
  

   which 
  interpretations 
  derived 
  from 
  it 
  enter 
  into 
  various 
  geologic 
  concepts 
  not 
  recognized 
  

   as 
  its 
  offspring, 
  are 
  chiefly 
  due 
  to 
  the 
  explicit 
  teachings 
  of 
  the 
  old 
  masters 
  who 
  had 
  clear 
  

   cosmological 
  conceptions 
  and 
  the 
  courage 
  of 
  their 
  convictions. 
  Foremost 
  of 
  these 
  among 
  

   Americans 
  was 
  Dana, 
  and 
  as 
  I 
  once 
  believed 
  and 
  taught 
  this 
  view 
  but 
  have 
  become 
  an 
  

   apostate 
  from 
  it 
  and 
  the 
  protagonist 
  of 
  another 
  view, 
  I 
  trust 
  that 
  in 
  following 
  Dana's 
  

   statement 
  in 
  the 
  fourth 
  edition 
  of 
  his 
  Manual 
  of 
  Geology 
  as 
  a 
  standard 
  exposition 
  I 
  

   shall 
  not 
  be 
  doing 
  any 
  injustice 
  to 
  the 
  inherited 
  view. 
  

  

  On 
  the 
  other 
  hand, 
  the 
  only 
  accretional 
  view 
  that 
  has 
  been 
  carried 
  out 
  into 
  any 
  

   measure 
  of 
  detail 
  is 
  the 
  planeteslmal 
  hypothesis. 
  (The 
  most 
  recent 
  statement 
  of 
  points 
  

   pertinent 
  to 
  this 
  discussion 
  may 
  be 
  found 
  in 
  a 
  series 
  of 
  articles 
  entitled 
  " 
  Diatrophism 
  

   and 
  the 
  formative 
  processes," 
  I 
  to 
  XV, 
  Jour. 
  Geol., 
  Vols. 
  XXI 
  (1913) 
  to 
  XXIX 
  (1921), 
  

   particularly 
  Articles 
  X 
  to 
  XV.) 
  To 
  clear 
  the 
  air 
  of 
  needless 
  fog 
  let 
  it 
  be 
  noted 
  that 
  this 
  

   is 
  not 
  a 
  speculation 
  regarding 
  the 
  origin 
  of 
  the 
  universe, 
  or 
  of 
  the 
  stars, 
  or 
  even 
  of 
  our 
  

   sun. 
  It 
  is 
  merely 
  an 
  endeavor 
  to 
  explain 
  the 
  singular 
  dynamic 
  properties 
  of 
  the 
  earth 
  

   and 
  its 
  fellow 
  planets 
  and 
  their 
  strange 
  relations 
  to 
  the 
  sun. 
  It 
  is 
  merely 
  a 
  definite 
  

   endeavor 
  to 
  solve 
  a 
  very 
  definite 
  problem. 
  It 
  started 
  from 
  an 
  attempt 
  to 
  test 
  the 
  ten- 
  

   s', 
  bility 
  of 
  the 
  inherited 
  view 
  of 
  the 
  atmosphere 
  just 
  outlined. 
  The 
  hypothesis 
  that 
  the 
  

   atmosphere 
  once 
  held 
  as 
  vapor 
  all 
  the 
  water 
  of 
  the 
  ocean 
  and 
  much 
  other 
  volatile 
  ma- 
  

   terial 
  was 
  framed 
  before 
  the 
  nature 
  of 
  gases 
  was 
  known. 
  The 
  view 
  seemed 
  logical 
  

   enough 
  under 
  the 
  old 
  notion 
  of 
  gases. 
  Special 
  reasons 
  for 
  testing 
  it 
  by 
  the 
  kinetic 
  theory 
  

   of 
  gases 
  arose 
  out 
  of 
  the 
  relations 
  of 
  the 
  atmosphere 
  to 
  glaciation. 
  The 
  results 
  of 
  the 
  

   test 
  were 
  very 
  unfavorable. 
  It 
  seemed 
  wholly 
  improbable 
  under 
  the 
  kinetic 
  constitution 
  

   of 
  gases 
  that 
  a 
  molten 
  earth 
  could 
  hold 
  so 
  vast 
  and 
  active 
  an 
  atmosphere. 
  This 
  adverse 
  

   result 
  led 
  to 
  other 
  tests 
  of 
  a 
  more 
  mechanical 
  sort. 
  These 
  disclosed 
  certain 
  critical 
  facts 
  

   in 
  the 
  dynamics 
  of 
  the 
  solar 
  system 
  which, 
  while 
  not 
  altogether 
  unknown, 
  had 
  not 
  been 
  

   adequately 
  recognized 
  as 
  indispensable 
  criteria 
  in 
  the 
  interpretation 
  of 
  our 
  planery 
  

  

  